1. Field of the Invention
The present invention relates to a plating apparatus for wet-plating objects, and more particularly, it relates to a plating apparatus having improved means for moving objects to be plated.
The present invention can be employed for plating various objects such as chip-type electronic components, for example.
2. Description of the Background Art
In general, a barrel plating apparatus is known as a plating apparatus for forming plating layers on external electrodes which are provided on chip-type electronic components. In the barrel plating apparatus, a plating solution, conductive media such as steel balls and objects to be plated are introduced into a cylindrical barrel, which in turn is rotated for electroplating the objects.
When such a barrel plating apparatus is employed, however, the media are also plated, to result in the following problems: (1) A relatively long time is required for plating the objects, (2) it is necessary to mix/separate the media and the objects with/from each other, and (3) the cost is relatively increased due to requirement for a large number of media.
In order to solve these problems of the barrel plating apparatus, Japanese Patent Publication No. 61-14237 (1986) proposes an apparatus for plating chip-type electronic components by placing the same on a cathode consisting of a metal mesh member. The plating apparatus described in this gazette is now described with reference to FIG. 1.
This plating apparatus 1 has a plating solution container 3 storing a plating solution 2. A cathode 4 is dipped in the plating solution 2. The cathode 4, which is formed by a metal mesh member, is suspended by suspenders 5 and 6, to be dipped in the plating solution 2. Further, an anode 7 is also dipped in the plating solution 2, so that a voltage is applied across the anode 7 and the cathode 4 for performing electroplating.
In addition, a vibrating part 8a of an ultrasonic vibrator 8 is dipped in the plating solution 2, for vibrating the plating solution 2 as well as the cathode 4. Namely, the cathode 4 which is simply suspended by the suspenders 5 and 6 is vibrated by the vibration applied from the ultrasonic vibrator 8. Consequently, chip-type electronic components 9 which are placed on the cathode 4 are slid on this cathode 4. The chip-type electronic components 9 are moved on the cathode 4 for changing contact portions between parts of the chip-type electronic components 9 requiring plating and the cathode 4, thereby reliably forming plating layers on the parts requiring plating.
The aforementioned gazette also discloses a structure of vibrating the cathode 4 by another vibrator which can apply physical vibration in place of the ultrasonic vibrator 8, thereby moving the chip-type electronic components 9 on the cathode 4.
The plating apparatus 1 disclosed in the aforementioned prior art is adapted to apply microvibration for sliding the chip-type electronic components 9, which are objects of plating, on the cathode electrode 4, thereby plating the same. However, when the plating is carried out at a high speed for forming plating layers of 3 .mu.m in thickness in about 5 minutes, for example, the chip-type electronic components 9 may disadvantageously adhere to each other or to the cathode 4 through plating films.
When the applied vibration is at a high frequency, further, movement of the chip-type electronic components 9 cannot follow that of the cathode 4 and the contact time of the chip-type electronic components 9 and the cathode 4 is so extremely reduced that the plating speed is remarkably reduced.